In mandarin nectars with different level of fruit (50, 65, 80, 100 %) produced from cultivar Kuno, total phenols, flavonoids, nonflavonoids and antioxidant activity were determined. The mentioned nectars were produced without and with 0,2 % of ascorbic acid, and in those nectars the stability of phenolic compounds during storage was investigated. Total phenols, flavonoids and nonflavonoids were determined with spectrophotometric method. Antioxidant activity was conducted by method for evaluation of free radical-scavenging activity of food by using 1,1-diphenyl-2-picrylhydrazyl. All investigated mandarin nectars showed remarkable antioxidant activity. After the storage of 45 days at 4 °C temperature, concentration of phenolic compounds minimized in all mandarin nectars. The obtained data indicate the minor role of added shore of ascorbic acid on antioxidant activity of mandarin nectars during storage.